It has been previously proposed to provide vehicle engine exhaust gas treatment with electrical discharge methods utilizing plasmasurface interactions to lower concentrations of hydrocarbons and NO and NOx in exhaust gas streams. The system involves a plasma chamber formed within an electrically insulated container packed with an inner bed of glass beads or the like and having an electrical charge applied between positive and negative electrodes which generate a plasma reaction within the chamber. It is believed that practical application of this concept to actual vehicle exhaust gas emission control has yet to be made.